Swelling Delay Cover for a Packer

ABSTRACT

A swelling packer is covered with a material that is preferably in a tubular form and slipped over the swelling element to be shrink fit with applied heat. The material is formulated to break down at temperatures slightly below the expected downhole temperatures so that ideally the packer has about 48 hours of swelling delay which is normally a time period long enough to allow it to be properly located without it swelling so much as to cause it to be damaged by running in. Various polymers can be used to make an imperious covering for run in that on the way starts to break down. Ideally the material for the cover disappears about the time of sealing or shortly thereafter.

PRIORITY INFORMATION

This application is a divisional application claiming priority from U.S.patent application Ser. No. 12/185,208, filed on Aug. 4, 2008.

FIELD OF THE INVENTION

The field of this invention is packers that swell and more particularlyouter coverings that delay their swelling to allow time for properplacement in the wellbore.

BACKGROUND OF THE INVENTION

Packers are used downhole for isolating zones in a wellbore. There areseveral styles available. Some of the more established designs feature ahydraulically or mechanically set design involving one or more sets ofslips that are ramped out for anchoring the packer body while thesealing element is compressed to extend radially to the surroundingtubular with the slips holding the set position. Another style that hasbeen used is the inflatable which has been run into casing, throughtubing and in open hole applications. In this design the element has afixed end and a movable end so that the fluid that inflates the elementcauses it to get larger radially for sealing contact while shrinkinglongitudinally. A system of valves retains the charging fluid andprevents overpressure of the element. Other designs have a sealingelement on the outside of the mandrel and use radial expansion fromwithin the mandrel. Some designs more recently have started usingmaterials that swell in response to exposure to fluids already in thewellbore or added later on. Other designs have used shape memorymaterials to take advantage of the ability of such materials to revertto different shapes when raised above the transition temperature. Shapememory alloys are selected for the sealing element or other componentssuch as springs that act on the slips or sealing element when the packeris set.

Among the swelling packers there continues to be a problem with delay ofswelling long enough to allow the swelling packer to be properlypositioned before it has swollen so much that it cannot be advanced tothe proper location because it has already swollen too much. Onesolution that has been tried is to put an outer layer of a material thatswells less than the core material and regulate the rate that wellfluids diffuse through the outer layer before they can reach the corethat swells at a significantly faster rate. This design is illustratedin U.S. Pat. No. 7,143,832. Some packers feed the fluid for swellingthrough the tubing instead of the well annulus where the packer is set.These designs also have a cover on the exterior that serves as thesealing component. There is no active external force that compresses theswelling element that ultimately drives the surrounding element intosealing contact in the wellbore. These designs are shown in U.S. Pat.Nos. 2,849,070 and 2,945,941. More recently in November 2007, theinventors of the present invention invented a coating for a swellingelement packer with a resin with hardener fiberglass material known asBondo® Product No. 402 made by the Bondo Corporation a subsidiary of 3MCorporation that is available at Wal-Mart. This product is a fiberglassresin that is mixed with a hardener and was brushed on without thefiberglass mat material as a test of whether it would delay swelling. Itwas allowed to air dry before running the packer into the well. Thistechnique was labor intensive and the fiberglass epoxy resin had a veryshort pot life making the consistency of the coating variable and whilehaving some benefit in retarding swelling the nature of the applicationprocess made it difficult to determine if there were beneficial resultseven after multiple runs with such a coating. Other packers have used acover on a compression set sealing element. In this application thepacker sealing element was selected for resistance to hydrogen sulfideand the material chosen also had the characteristic of swelling in oilbased mud. The cover was placed over the sealing element exterior andwhen the destination for the packer was reached the sealing element waslongitudinally compressed with the intent that the cover would bemechanically compromised as the sealing element was forced out. The factthat the element swelled was a downside in a decision controlled bytolerance to corrosive materials in the well and played no part in theactual sealing process. This type of packer is illustrated in U.S. Pat.No. 4,862,967.

The present invention seeks to make a swelling packer operate in hightemperature applications by covering it externally with an imperviouscover to allow sufficient time to get the packer to the desired positionbefore it swells to a point where it can not be advanced. The coating ispreferably formed into a tubular shape and shrink fit to the swellingelement. On the way down to the desired location the combination of thewell temperature and the well fluids attack the cover to the point thatideally when the packer is placed at the desired location in the wellthe cover has been attacked sufficiently for it to have to havedissolved or have pieces break off or will break down in a matter of afew hours or days so that the sealing due to swelling results in contactof the core material with the surrounding tubular or the wellbore wallin open hole. The material for the cover is expected to lose itsintegrity as opposed to remain intact and simply control well fluiddiffusion through it. The cover, when applied is impervious and itssurrounding fluid environment causes it to fail by several potentialmechanisms. These and other aspects of the present invention will bemore apparent to those skilled in the art from the description of thepreferred embodiment described below and the associated drawings, whilerecognizing that the full scope of the invention is determined by theclaims.

SUMMARY OF THE INVENTION

A swelling packer is covered with a material that is preferably in atubular form and slipped over the swelling element to be shrink fit withapplied heat. The material is formulated to break down at temperaturesslightly below the expected downhole temperatures so that ideally thepacker has about 48 hours of swelling delay which is normally a timeperiod long enough to allow it to be properly located without itswelling so much as to cause it to be damaged by running in. Variouspolymers can be used to make an imperious covering for run in that onthe way starts to break down. Ideally the material for the coverdisappears about the time of sealing or shortly thereafter.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a view of a tubular sleeve cover before it is applied to aswelling element;

FIG. 2 is the view of FIG. 1 showing the tube cover put over theswelling element and heat being applied; and

FIG. 3 is the view of FIG. 2 showing the tubular cover shrunk over theswelling element and in condition for running the packer in the hole.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 1 illustrates a tube shape 10 that is long enough to cover aswelling element 12 leaving an air gap 14 that allows rapid deployment.The swelling element 12, shown in FIG. 2, is preferably rubber mountedto a mandrel 16. It sets by radial swelling without longitudinalcompression. Heat source 18 can be a hand held unit or an oven thataccepts the assembly. Application of heat reduces the diameter of thecover material 10 so that it snugly fits to the element 12. The ends ofthe element 12 are also sealed with the tube shape 10 as a result of theheating.

The cover 10 can also be a film formed on the element 12 or applied toit as a sheet using a variety of wrapping techniques whose goal is toexternally cover the swelling element and to delay its exposure to wellfluids. This delay allows time to deliver the assembly to the desireddepth in the well without enough swelling that would potentially damagethe element 12 while it is still being advanced into the wellbore.

The goal is to have a tight fitting cover 10, as shown in FIG. 3, thatis impervious to well fluids but that is also attacked by thecombination or one of well temperature and well fluid compositions.Normally a period of about 48 hours is long enough to get the packerinto position where swelling of the element 12 creates a seal. Thematerial for the cover 10 is preferably sensitive to temperatures about10-30 degrees F. lower than the anticipated well fluid temperatures. Asa result the cover 10 begins disintegrating as early as during thepacker delivery phase. The objective is to use the element 12 swellingfor contact in the wellbore to an open hole or a surrounding tubular.Alternatively to fully relying on well fluid temperatures to attack thecover 10 the packer can carry a heat source 20 to initiate or hasten thefailure of the cover 10 along with a trigger actuated from the surfacesuch as by tubing or hydrostatic pressure or wired or other signaltransmission mechanism.

As opposed to the concept of diffusion, the cover 10 is intended toremain impervious until portions of it are either melted or dissolvedaway to gradually expose the element 12 directly to well fluids. Piecesmay also simply break off due to exposure to temperature or specificfluids in the well. The cover 10 especially in the shrink fit tubevariation goes on fast and is cost effective to manufacture and apply.It has no issues of shelf or pot life as with multi-component epoxieswith hardeners and is far less labor intensive even when manually rolledoff a roll in sheet form and over the element 12 in a single or multiplelayers that can partially or totally overlap. The film can be spirallywound with overlaps simply fusing together when heat is applied toshrink the cover onto the element 12. The preferred cover materials arepoly tetra fluoroethylene (PTFE), poly ethylene teraphthalate polyester(PET), poly vinyl alcohol (PVA), fluorinated ethylene propylene (FEP),per fluoro alkoxy (PFA) or ethylene tetra fluoro ethylene (ETFE) orcombinations thereof. The preferred element 12 material is rubber.

The cover 10 can be a single or multiple layer tube. If it is inmultiple layers it is preferred that the thermal sensitivities to heatincreases as the layers get closer to the element 12. It is notnecessary that the layers fuse together or that they seal tightly withrespect to each other. The multi-layer version of the cover 10 providesadditional protection against mechanical damage during run in and canprovide a staged response to thermal exposure as the outermost layerswill degrade earlier and at lower temperatures. The layers can besimilar in chemical structure with some variation in composition totailor the desired properties so that for example an outer layer willbegin degrading at 350 degrees F. while the layer under it will be goodfor about 400 degrees F. The layers can be shrink fit individually ortogether to the element 12.

As a result, a swelling packer is created with a thin outer cover whichdelays swelling to allow proper positioning. The process to apply thecover is simple and cost effective preferably using a tube shape andslipping it on and heating to shrink fit it to the underlying swellingelement. By the time the packer arrives to where it needs to seal thecover is breaking down or already broken down by either melting orsimply being chemically attacked so that the swelling can take place orcontinue and a seal is obtained at the desired location in a matter of afew days or weeks later. The film thickness can be adapted to the timeneeded for the delay of substantial swelling and the expected welltemperatures. Field application of the covers or different properties orthickness without skilled labor or complex tools is possible. The coveris cost effective and there is little to no waste material. Coverthicknesses of about 5-20 thousands of an inch are contemplated.Optionally, the cover 10 can be applied to the element 12 and then thetwo can be mounted to the mandrel 16 at a later time. The cover, in thatcase, can cover only the exterior surfaces of the element 12 or/and theinterior bore as well. Other options exist for using the film cover 10in conjunction with another cover 25 made of fiberglass resin withhardener, described above, or with alternative coatings to thefiberglass resin that degrade with exposure to temperatures and fluidsin the wellbore. In one variation the fiberglass resin cover 25 can beapplied to the element 12 initially and then a tubular cover 10 can beslipped over the resin coating for additional protection during run in.The coating 10 can be in one or more layers, described above, and ispreferably shrink fit. Alternatively, the fiberglass resin or equivalentcover 25 can be applied over a cover 10 that has previously been shrinkfit to the element 12 as shown in FIG. 3. In either arrangement theouter layer is degraded first generally at a lower temperature and theinner layer is degraded on further exposure over time to a highertemperature that reaches it when the outer layer degrades. While shrinkfitting the cover 10 is preferred, it can be mounted in other ways andclosed off, regardless whether it is the inner or outer covering to theelement 12.

The above description is illustrative of the preferred embodiment andmany modifications may be made by those skilled in the art withoutdeparting from the invention whose scope is to be determined from theliteral and equivalent scope of the claims below:

1. A downhole packer manufacturing and method of its use, comprising:applying a film cover to a swelling element mounted on a mandrel;exposing said cover to well fluids when running it downhole; using saidexposing to undermine the integrity of said cover; allowing said elementto swell without longitudinal compression from access of well fluidsthrough the undermined cover sealing downhole with said swellingelement.
 2. The method of claim 1, comprising: making said cover is inan elongated tubular shape; slipping said tubular shape over theswelling element; joining said tubular shape to the swelling element. 3.The method of claim 2, comprising: using heat for said joining.
 4. Themethod of claim 3, comprising: shrinking the dimensions of said tubularshape by using said heat.
 5. The method of claim 4, comprising: makingsaid cover from a material attacked by well fluids.
 6. The method ofclaim 5, comprising: making said cover of a material impervious to wellfluid for a predetermined time.
 7. The method of claim 6, comprising:making said material melt or dissolve at temperatures more than 10degrees F. lower than the well temperature at the desired settinglocation downhole.
 8. The method of claim 6, comprising: making saidmaterial melt or dissolve with exposure to well fluids for apredetermined time.
 9. The method of claim 7, comprising: making saidcover from one or more PTFE, PET, PVA, FEP, PFA or ETFE polymerfamilies.
 10. The method of claim 1, comprising: applying said filmcover to said swelling element before mounting the swelling element tosaid mandrel.
 11. The method of claim 1, comprising: applying said filmcover to said swelling element after the swelling element is mounted tosaid mandrel.
 12. The method of claim 1, comprising: using a film in asheet form; wrapping said sheet of film around said swelling element inat least one layer.
 13. The method of claim 1, comprising: applying heatto said film cover from a heat source supported by said mandrel.
 14. Themethod of claim 13, comprising: triggering said applying heat from asurface signal.
 15. A downhole packer manufacturing and method of itsuse, comprising: applying a cover made from a resin and hardenercombination to a swelling element mounted on a mandrel; exposing saidcover to well fluids when running it downhole; using said exposing toundermine the integrity of said cover; allowing said element to swellwithout longitudinal compression from access of well fluids through theundermined cover sealing downhole with said swelling element.
 16. Themethod of claim 15, comprising: using a fiberglass resin with hardenerfor said cover.
 17. The method of claim 16, comprising: using product402 made by the Bondo Corporation in said cover.
 18. The method of claim1, comprising: making said cover in multiple layers that degrade atdifferent temperatures.
 19. The method of claim 18, comprising: applyingsaid layers to said sealing element sequentially and shrink fitting eachlayer or all at once and shrink fitting all layers.
 20. The method ofclaim 18, comprising: making an inner layer degrade at a highertemperature than another layer covering it.
 21. The method of claim 1,comprising: applying a cover made from a resin and hardener combinationto said swelling element mounted on a mandrel, either below or outsideof said film cover; configuring said covers to degrade at differenttemperatures.